The lack of an obvious "band gap" is a formidable hurdle for making a nanotransistor from graphene. Here, we use density functional calculations to demonstrate to the first time that porosity such as evidenced in recently synthesized porous graphene (http://www.sciencedaily.com/releases/2009/11/091120084337.htm) opens a band gap. The size of the band gap (3.2 eV) is comparable to most popular photocatalytic Mania and graphitic C3N4 materials. In addition, the adsorption of hydrogen on Li-decorated porous graphene is much stronger than that in regular Li-doped oraphene due to the natural Separation of Li cations. leading to a potential hydrogen storage gravimetric capacity of 12 wt %. In light of the most recent experimental progress on controlled synthesis, these results Uncover new potential for the practical application of porous graphene in nanoelectronics and clean energy.